1. Field of the Invention
The present invention relates to an optical pickup device for use in reading information from and writing information on such optical discs as CDs (Compact Discs), DVDs (Digital Versatile Discs), and BDs (Blu-ray Discs; registered trademark) or to an optical-disc drive apparatus with such an optical pickup device.
2. Description of the Related Art
Conventional optical pickup devices or conventional optical-disc drive apparatuses with such optical pickup devices commonly employ such a structure as shown in FIG. 2. As illustrated in FIG. 2, the components of an optical system are glued to an optical pickup housing 9 that is made primarily of such a metal as Zn, Mg, and Al or PPS (polyphenylene sulfide) resin and shaped by die casting or molding.
FIG. 3 illustrates the optical path of an optical pickup. Light emitted from a light-emitting element 11 such as a laser diode and the like is guided onto an objective lens 15 through optical components such as a lens 12, a prism 13, a mirror (not shown), and the like. After the objective lens 15 focuses the light onto an optical disc 16, reflected light from the optical disc 16 travels through optical components such as the objective lens 15, other lenses, a mirror, and the like to a photodiode 17, where the reflected light is converted into an electric signal.
Different optical recording medium, such as CDs, DVDs, and BDs, require different wavelengths of light sources, different light protective-layer thicknesses, and different numerical apertures (NA) of objective lenses. For this reason, an optical pickup device requires, in addition to an objective lens, a correcting mechanism for spherical aberration so that the optical pickup device can handle optical discs of various formats.
Specifically, correction of spherical aberration requires a movable lens 14 to be placed between the objective lens 15 and the prism 13 as shown in FIG. 3 and also requires the use of a lens mover 10 as shown in FIG. 2 so that the position of the movable lens 14 can be finely adjusted in a direction of its optical axis.
The lens mover 10 employs such a structure as disclosed in JP-2009-4013-A (Patent Document 1). FIG. 4 also illustrates in perspective the lens mover 10 that moves the movable lens 14.
As shown in FIG. 4, the movable lens 14 is secured to one end of a lens support member 15 that is formed of synthetic resin whose coefficient of friction is low (i.e., abrasion-resistant). A frame 16 is integrally formed with the lens support member 15. The frame 16 is located at the middle section of the lens support member 15 and hollow in a direction of the optical axis of the movable lens 14. The proximal-end side of the frame 16 which is located opposite the movable lens 14 is provided with an auxiliary-shaft holding member 17. The auxiliary-shaft holding member 17 has a U-shaped vertical cross-section and is formed integrally with the frame 16.
A drive shaft 18 is inserted into the frame 16 so as to penetrate the frame 16, and an auxiliary shaft 19 is inserted into the U-shaped portion of the auxiliary-shaft holding member 17 in a slidable manner. The drive shaft 18 and the auxiliary shaft 19 are arranged parallel to each other. The lens support member 15 and the movable lens 14 are jointly moved by the drive shaft 18 and the auxiliary shaft 19 in a direction of the optical axis of the movable lens 14.
Provided inside the frame 16 are, in addition to the drive shaft 18, a press member 20 and a spring. The spring is inserted between the press member 20 and an inner side wall of the frame 16. The press member 20 presses the drive shaft 18 with the aid of the spring to such an extent that the frame 16 can slide on the drive shaft 18.
A pair of drive-shaft support walls 22a and 22b is arranged on a base member 21 so as to face each other with a given space provided therebetween. Likewise, a pair of auxiliary-shaft support walls 23a and 23b is arranged on the base member 21 so as to face each other with a given space provided therebetween. One end and the other end of the drive shaft 18 are loosely supported by a guide hole 24a of the drive-shaft support wall 22a and by a guide hole 24b of the drive-shaft support wall 22b, respectively, such that the drive shaft 18 can slide in its shaft-extending direction. In contrast, one end and the other end of the auxiliary shaft 19 are secured to the auxiliary-shaft support walls 23a and 23b, respectively.
For the purpose of increasing the slidability of the shaft contact portions of the auxiliary-shaft holding member 17, the press member 20 and the like with respect to the drive shaft 18 and the auxiliary shaft 19, a lubricant is often applied to the drive shaft 18 and the auxiliary shaft 19. A typically used lubricant is grease or oil made primarily from olefin-based synthetic oil, fluorine resin, silicone resin, or the like.
Although applying such a lubricant to the shafts 18 and 19 enhances the slidability of the movable lens 14, the operation of the lens mover 10 often results in that lubricant being scattered, being attached to the housing walls of the lens mover 10, or being spilled out, which may contaminate other optical components.
JP-11-176115-A (Patent Document 2) discloses a structure that prevents lubricant from being scattered while a lens mover of an optical pickup device is in operation.